Dragonfly: Contemplating a Return to Titan

byPaul GilsteronDecember 27, 2017

Our continuing interest in Titan as a possible venue for life was energized last year with the publication of a paper by Martin Rahm and Jonathan Lunine, working with colleagues David Usher and David Shalloway (all at Cornell University). I’ve written about this one before (see Prebiotic Chemistry on Titan?) and won’t revisit the details, but the gist is that hydrogen cyanide produced in Titan’s atmosphere can condense into aerosols that are transformed into interesting polymers on the surface. Of these, the most intriguing seems to be polyimine.

The authors see polyimine as capable of producing complex, ordered structures that absorb light, producing energy that can be used to catalyze prebiotic chemistry. Rather than looking in Titan’s seas, the authors think we’ll find hydrogen cyanide reactions in tidal pools on the shores near seas and lakes. It’s an interesting proposition, and like so many notions about Titan, it requires us to get a payload back to the surface, as we did in 2005 with Huygens. But this time, we’ll want to have extended survivability on Titan and a full suite of instruments.

Image: This composite was produced from images returned on 14 January 2005, by ESA’s Huygens probe during its successful descent to land on Titan. It shows the boundary between the lighter-coloured uplifted terrain, marked with what appear to be drainage channels, and darker lower areas. These images were taken from an altitude of about 8 kilometres with a resolution of about 20 metres per pixel. Credits: ESA/NASA/JPL/University of Arizona.

Thus the news that Dragonfly has won approval as a finalist concept for a robotic launch to Titan in the mid-2020s is encouraging. Dragonfly offers not just a useful instrument package but mobility on the surface in the form of a rotorcraft that could explore numerous sites on the moon. We have to be creative indeed in imagining life that would exist at -180 degrees Celsius in an environment that gets a tenth of one percent of the sunlight Earth’s surface receives. But as Rahm, Lunine and colleagues have reminded us, mechanisms may exist to make it happen.

Elizabeth Turtle (JHU/APL) is lead investigator on Dragonfly, with APL providing project management. The concept involves an eight-bladed drone — two rotors at each of its four corners — capable of sampling widely. Dragonfly would be able to look at prebiotic chemistry of the kind Rahm and Lunine have studied, selecting sites with varying geology and surface composition.

Another key issue for the lander: Is there exchange of organics between the surface and Titan’s interior ocean? Using a Multi-mission Radioisotope Thermoelectric Generator (MMRTG) for power, Dragonfly should be capable of remaining operational not just for months but for years in answering these questions.

Image: Dragonfly is a dual-quadcopter lander that would take advantage of the environment on Titan to fly to multiple locations, some hundreds of kilometers apart, to sample materials and determine surface composition to investigate Titan’s organic chemistry and habitability, monitor atmospheric and surface conditions, image landforms to investigate geological processes, and perform seismic studies. Credit: NASA.

NASA’s competitive peer review process whittled a dozen proposals submitted under the New Frontiers program announcement of opportunity down to a final two, the other being a Comet Astrobiology Exploration Sample Return (CAESAR). Here we’re talking about a return to 67P/Churyumov-Gerasimenko, following up the European Space Agency’s highly successful Rosetta mission. Both CAESAR and Dragonfly will receive funding through the end of 2018. One of the concepts will be selected the following year for subsequent mission phases.

Expect more on CAESAR in an upcoming article. The Rahm et al. paper mentioned above is “Polymorphism and electronic structure of polyimine and its potential significance for prebiotic chemistry on Titan,” published online by Proceedings of the National Academy of Sciences 4 July 2016 (full text). Matt Williams interviews Elizabeth Turtle about Dragonfly in a fine Universe Today article from May of this year.

I wouldn’t say ‘quite dark.’ My understanding is that light levels on Titan’s surface are 350 times brighter than moonlight on Earth under a full moon. That’s a tiny fraction (about one thousandth) the daylight brightness on Earth’s surface. I don’t have background on how Huygens adjusted for ambient light levels, but maybe someone else can weigh in.

I know Huygens had a spotlight. The light patch can be seen in the lower corner of its landing image.

The Soviet Venus landers Venera 9 and 10 had floodlights due to the Venera 8 lander measurements indicating the surface of the second planet from Sol was rather dark. Turns out Venera 8 had landed when Sol was only 5 degrees above its horizon: The daylight levels on Venus were actually about the same as a bright overcast day on Earth, as Venera 9 and 10 and then Venera 13 and 14 revealed.

For me, the nagging question is: if this Dragonfly finds life (or something resembling it), will it be able to deliver enough scientific evidence to make it anything more than speculation?
Personally, I doubt if the discovery of extraterrestrial life will be verifiable without a sample return to Earth.
So I expect nothing more than a 40-year wait for a mission that discovers nothing more than interesting chemistry.

Experiment to find life will be very hard to design, instrument for our type of life will not work.
And we do not quite know how to design an experiment for Titan.
I will be very happy for ‘interesting chemistry’ – then we could start to design the actual instrument!
Then perhaps one that simply look for metabolism – but it will need to be kept very cold, or we ‘cook’ the organism.

The other good option for exploring Titan that I have heard is a hot air dirigible, with the heat for inflating the balloon part coming from an RTG or a nuclear reactor. Does anyone know what factors pushed the decision to a helicopter rather than a lighter than air craft?

Jim, the team evidently wanted to choose a mission that could accomplish both wide-ranging movement (as with a balloon) and also analysis up-close of surface features, with the possibility of sampling. The idea is to get the best of both methods with this concept.

While I am hopeful this project will be finally chosen, I am wondering about all of this moving parts functioning in the extremely cold atmosphere over extended periods. Questions about survivability of the instruments will surely be put to the team, questions perhaps sufficient to choose a different project.

I don’t see discussion about the amount of time this critter would be able to spend.

Nice plan. Seems pretty audacious for the NASA of late. I wonder about long term material stability of stressed propulsion components at -180°C.
Shame that ELF was again not selected. And doubly sad that Rossettas Philae was unable to fully use COSAC. That failure possibly gave the critical extra kick to select CAESAR as one of the two finalists.

It’s should be noted that irrespective of the “tidal pool” theory mentioned above, Dragonfly is slated to fly exclusively in dry equatorial regions. No direct shoreline sampling is being considered afaik. JHAPL offers a summary of their plan here. http://dragonfly.jhuapl.edu/docs/DragonflyTechDigestAPL.pdf

Thank you for this info. It is very disappointing : going all that way and just fly in the desert. Maybe, during an extended mission, they’ll try something more exciting but it’s a very long way from the equator to any of the lakes. Hopefully there will be some more interesting landmarks than the dunes.

Apropos dunes. I don’t want to overemphasise this since there is no consensus yet. However, there are potentially catastrophic risks involved exactly due to this missions stated goal to examine the dunes given it’s particular sampling and propulsion methods.
The potential source of danger can be found in a posited explanation for the apparent resistance of the dunes to the presumed prevailing winds. And that is that they are highly electrostatically charged. Primitive simulations have given this some credence amongst researchers. More work is needed.
Here a questionable response from RD Lorenz one of the missions organisers at APL:
“There is a basic principle of spacecraft design that you have to harden electronics against electrostatic discharge. Now, we would obviously pay attention to the sort of erosion or deposition considerations that blowing sand can introduce, but this is something that is more or less familiar. The Huygens probe landed on the surface of Titan and didn’t instantly go dark with stuff sticking to it…. Anytime one goes to an alien environment, one must be cautious, but we’re not concerned.”
The comparison with Huygens is disingenuous at best. Huygens did not have eight rotary airfoils with their associated capacity to distribute charged material or even increase the electrostatic potential. These rotors will not only provide propulsion. They are intended as the sole method of material excavation during sampling. A mass accumulation of charged particulate could easily scuttle the mission.

If those polyimine structures are a different type of precursor to life, and if they exist on Titan, I’m sure the chemists, biochemists and molecular biologists will be engaged for years exploring them.

Titan is a unique world to allow the use of such a probe that relies on a dense atmosphere, a solid or liquid surface to land on, and temperatures cool enough for a probe to continue operating.

I do wonder whether adding a lift envelope to reduce the lift requirement of the rotors might help or hinder the probe’s operations. Such a design might be adaptable for submersible operation on Titan and the sub-surface oceans of the icy moons.

Why the coy attitude toward finding life on Titan, is this Mars 2.0
redux, with Planetary science groups afraid of a definitive null result
and getting funding cutoff as a reward .

It cant be that expensive to create a simple test for life in tidal pools of Titan. Create sample “feed bags” with a variety compounds we speculate a lifeform on Titan would need. Better go with both Light using life and Chemical redutive life “Buffets” and place them in contact with the tide pools, see what is consumed.

Unfortunate it is so difficult to send probes to Saturn space.
Surely if you spend So much on propulsion, adding to the mothership the capability of entering of an Enceladous orbit and dropping (landing) sampling buoys there, is worth the effort

I hope this mission happens. Titan is more interesting in Mars in many ways. I hope that the drone has on-board microscopes as well as altered plans for visiting the shoreline of a sea or lake. Scientific or not, obtaining video and photos of Titan’s liquid surfaces, with possible waves and other activity should not be missed. Plus, microscopic and spectroscopic examination of the liquid is also too good to pass up on.

I wonder how they’re going to get rid of waste heat from RTGs and not damage the environment and the samples. Just imagine, water-based lifeforms are lava monsters in the world of liquid methane, and their authomated missions still are robots from hell, if not designed carefully…

10s and 100s of watts are modest by our standarts, with heat fluxes of hundreds w/m^2, but on Titan and other cryogenic worlds, IR from heat exchangers would be a factor to consider. Imagine an alien probe with 200-400oC exterior, red-hot interior and incadescent white heat exchangers trying to sample some grass by the lake in the forest, especially at night…

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last eleven years, this site has coordinated its efforts with the Tau Zero Foundation, and now serves as the Foundation's news forum. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi).

Centauri Dreams publishes selected comments on the articles under discussion here. The primary criterion is that comments contribute meaningfully to the debate. Among other criteria for selection: Comments must be on topic, directly related to the post in question, must use appropriate language and must not be abusive to others. Civility counts. In addition, a valid email address is required for a comment to be considered. Centauri Dreams is emphatically not a soapbox for political or religious views submitted by individuals or organizations. A long form of the policy can be viewed on the Administrative page. The short form is this: If your comment is not on topic and respectful to your fellow readers, I'm probably not going to run it.